A hand scaler is widely used as a hand tool for removing dental calculus and the like. A hand scaler as shown in FIG. 14 and designated as 1, may be segmented into a grip section 2 which is grasped by an operator, shank sections 3 which are contiguously provided usually at the ends of the grip section 2 and bent as required, and blade sections 4 each of which is provided at the tip of each shank section 3. One of the blade sections 4, which are double-edged, is shown enlarged and in section in FIGS. 15 and 16, respectively. The blade section 4 has an inner face 4a, right and left sides 4b, and a curved back face 4c. The inner face 4a and each of the right and left sides 4b form a sharp edge, which substantially functions as a cutting edge 5 for removing dental calculus or for performing other treatments.
When the cutting edge 5 becomes dull as a result of use, the edge 5 can hardly catch calculus, resulting in decreased treatment efficiency. In addition, the operator is likely to exert excess force to the scaler 1 to cause wound in the gum or periodontal tissues of a patient or to cause damage to the scaler 1. For obviating such danger, the cutting edge 5 has to be restored by proper sharpening with a grindstone.
Conventional methods for restoring the cutting edge may be divided into manual sharpening wherein a surface of a grindstone in the form of a rectangular plate is placed to the side 4b of the scaler blade section 4, and moved up and down along the side 4b with a hand, and motor-assisted sharpening wherein a grindstone in the form of a circular disk is rotated by a motor, and the side 4b of the blade section is held to the peripheral surface of the grindstone.
The manual restoration of the cutting edge is carried out with the scaler 1 in one hand and the grindstone in the other hand, adjusting the angle of the grindstone surface to the inner face 4a in conformity with the angle of the cutting edge 5. It is thus much more laborious than the motor-assisted sharpening, and is particularly difficult for an inexperienced beginner. Even the angles adjusted by skilled operators may have individual difference, and the finishing may not be uniform.
Restoration of the cutting edge by the motor-assisted sharpening also has problems. For example, the side 4b of the blade section is sharpened with the curved outer peripheral surface of a grindstone, so that restoration of the cutting edge to exactly the original angle before wearing is hard to achieve, compared to the manual sharpening using a flat grindstone surface. This, in combination with continuous rotation of the grindstone, often leads to excess grinding of the scaler.